doc/develop/sending_patches.rst: Clarify when to use which branch

The previous wording on the paragraph about what branch to use when
submitting patches did not reflect how / when the next branch is
currently used. Reword this to note that master should be used for bug
and regression fixes, always, and that next should be used once it
opens, with -rc2.

Reported-by: Jerome Forissier <jerome.forissier@linaro.org>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
Acked-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/doc/develop/sending_patches.rst b/doc/develop/sending_patches.rst
index 3f25b1d..9308f42 100644
--- a/doc/develop/sending_patches.rst
+++ b/doc/develop/sending_patches.rst
@@ -73,12 +73,14 @@
      cover letter why they are ignored is desired.
 
 * Send your patches as plain text messages: no HTML, no MIME, no links, no
-  compression, no attachments. Just plain text. The best way the generate
-  patches is by using the ``git format-patch`` command. Please use the
-  ``master`` branch of the mainline U-Boot git repository
-  (``https://source.denx.de/u-boot/u-boot.git``) as reference, unless (usually
-  late in a release cycle) there has been an announcement to use the ``next``
-  branch of this repository instead.
+  compression, no attachments. Just plain text. The best way to generate
+  patches is by using the ``git format-patch`` command. For a patch that is
+  fixing a bug or regression of some sort, please use the ``master`` branch of
+  the mainline U-Boot git repository
+  (``https://source.denx.de/u-boot/u-boot.git``) as reference. For new
+  features, if the ``next`` branch has been opened (which happens with the
+  release of ``-rc2``) that branch should be used, otherwise ``master`` is
+  acceptable.
 
 * Make sure that your mailer does not mangle the patch by automatic changes
   like wrapping of longer lines etc.